Star-branched polymer with dendrimer core

ABSTRACT

Polyisobutylene (PIB) functionalized with terminal reactive unsaturation is disclosed. Carbocationically polymerized monohalogen-terminated PIB is dehydrohalogenated in a hydrocarbon solvent using an alkoxide of the formula RO-M wherein R is alkyl of at least 5 carbon atoms and M is alkali metal. The PIB obtained has terminal unsaturation which is 100% in the reactive ‘exo’ form which can be converted to succinic anhydride groups (PIB-SA) by the ene reaction with maleic anhydride. The PIB-SA is reactive with amine functional dendrimers to obtain a star-branched polymer having a dendrimer core and PIB branches joined by succininide linkages. Blends of the star-branched polymer with polypropylene have improved energy absorption properties and controllable moisture/oxygen permeabilities useful in films.

This application is a Continued Prosecution Application of U.S. patentapplication Ser. No. 09/100,271, filed Jun. 19, 1998, this applicationclaims benefit of provisional application Ser. No. 60/050,727, filedJun. 25, 1997.

FIELD OF THE INVENTION

The present invention relates to a method for preparing polyisoolefinshaving exclusive ‘exo’ terminal double bond chain ends, thepolyisoolefins having exclusive ‘exo’ terminal double bonds, a methodfor preparing a star-branched polymeric material from the polyisoolefinand a dendrimer, and the functionalized polyisobutylenes and thestar-branched polymeric materials prepared by these methods. The presentinvention also relates to blends of polyolefins and the star-branchedpolymer, and films and fibers made from these blends. The presentinvention also relates to a method for preparing star-branched polymericmaterial from a polyolefin and a hydrolytically stable dendrimer and thestar branched material prepared by this method.

BACKGROUND OF THE INVENTION

Dendrimers are well defined globular molecules. These are generallyprepared by stepwise or reiterative reaction of multifunctional monomersto obtain a branched structure. In U.S. Pat. No. 5,530,092, for example,the repetition of double Michael addition of acrylonitrile starting witha primary diamine followed by hydrogenation obtains two primary aminesfor each initial amine. This doubles the number of primary amine groups.Thus, beginning with a diamine, the first generation dendrimer (G1) hasfour primary amines; the second generation (G2) has eight primaryamines; the third generation (G3) has sixteen primary amines; the fourthgeneration (G4) has thirty-two primary amines; the fifth generation (G5)has sixty-four primary amines in the outer shell, and so on. Thesepolyamine dendrimers are said to be stable to degradation throughhydrolysis reactions.

Amine-terminated polyamidoamine, polyethyleneimine andpolypropyleneimine dendrimers are also known, for example, from U.S.Pat. Nos. 5,393,797; 5,393,795; 5,560,929; and 5,387,617, all toHedstrand et al.

Polyisobutenyl succinimide-polyamidoamine dendrimer star-branchedpolymers obtained by reacting second generation polyamidoaminedendrimers with polyisobutenyl succinic anhydride are disclosed inMigdal's U.S. Pat. No. 4,938,885 [to Migdal]. These polymers are said tohave dispersancy powers in lubricating oils and to exhibit antioxidantactivity. However, these products are not hydrolytically stable.

U.S. Pat. No. 5,316,973 discloses telechelic olefin polymers such astelechelic diolefin polyisobutylene prepared by refluxing dihalogenpolyisobutylene in tetrahydrofuran with a strong base such as potassiumt-butoxide. This is said to produce a product which has ¹H NMRspectroscopy at 60 MHz consistent with a terminal vinylene functionalityof 2.0.

Boerzel et al., U.S. Pat. No. 4,152,499, discloses polyisobutylene saidto contain a proportion of double bonds reactive with maleic anhydrideof from 60 to 90 percent of the double bonds present in thepolyisobutylene. The polyisobutylenes are prepared using a borontrifluoride polymerization initiator with a short polymerization time.

Bronstert et al., U.S. Pat. No. 4,599,433, discloses the preparation ofpolyisobutylene-succinic anhydrides with titanium, zirconium or vanadiumalkoxides as catalysts which are said to isomerize polyisobutyleneduring the reaction making it more reactive with the maleic anhydride.The polyisobutylene-succinic anhydride adduct is in turn reacted with apolyamine to obtain a lubricating oil additive.

SUMMARY OF THE INVENTION

The present invention arises, in part, from a method for preparingpolyisobutylene having reactive terminal vinylidene groups. The processinvolves dehydrohalogenating halogen-terminated polyisobutylene in ahydrocarbon solvent using a metal alkoxide soluble in the hydrocarbonsolvent. This method does not require tetrahydrofuran (THF) as asolvent. This obtains a polyisobutylene terminated with an unsaturatedend group which is in the reactive ‘exo’ form, and free of thecorresponding ‘endo’ form. This method avoids the use of the undesirabletetrahydrofuran as a solvent. The presence of tetrahydrofuran rendersthe dehydrohalogenation reaction insufficiently stereospecific andintroduces the possibility of peroxide formation.

In one aspect, the present invention comprises a method for preparing apolyisoolefin having double bond chain ends exclusively in the ‘exo’form. The method includes the step of dehydrohalogenating thehalogen-terminated polyisoolefin in a hydrocarbon solvent in thepresence of hydrocarbon-soluble alkoxide. The halogen-terminatedpolyisoolefin is generally obtained by carbocationically polymerizingthe isoolefin in the presence of a halogenating initiator according totechniques well known in the art to obtain halogen-terminatedpolyisoolefin. The preferred alkoxides are represented by the formulaRO-M wherein R is alkyl of at least 5 carbon atoms and M is alkalimetal. The polyisoolefin obtained from the carbocationic polymerizationprocess can be telechelic, or in one embodiment ismonohalogen-terminated. The isoolefin preferably has from 4 to about 12carbon atoms, and more preferably is isobutylene. The alkoxide ispreferably a branched alkoxide, more preferably tertiary-pentoxide(t-pentoxide), and the alkali metal can be one of lithium, sodium,cesium, rubidium, preferably potassium. The solvent should beessentially free of tetrahydrofuran. The method thus effected inaccordance with the invention obtains polyisobutylene having a terminaldouble bond chain end in ‘exo’ form, essentially free of ‘endo’ form.

In another aspect, the invention comprises a method for preparing astar-branched polymeric material having a hydrophilic dendrimer core andhydrophobic polyolefin branches. The method includes reactingpolyisoolefin-succinic anhydride with a dendrimer having primary aminefunctionality. The polyisoolefin-succinic anhydride is preferablypolyisobutylene-succinic anhydride (PIBSA), most preferably prepared bythe steps of: (1) carbocationically polymerizing isobutylene in thepresence of a halogenating initiator, such as 2,4,4-trimethylpentylchloride, to obtain monohalogen-terminated polyisobutylene; (2)dehydrohalogenating the monohalogen-terminated polyisobutylene in ahydrocarbon solvent in the presence of soluble alkoxide represented bythe formula RO-M, R being an alkyl of at least 5 carbon atoms and Mbeing an alkali metal; and (3) functionalizing the dehydrohalogenatedpolyisobutylene with maleic anhydride.

The star-branched polymer preparation preferably includes preparing thedendrimer by the steps of: (1) forming the double Michael additionproduct of acrylonitrile or methyacrylonitrile with a primary polyamine;(2) hydrogenating the double Michael addition product from step (1) toform primary polyamine functionality; and (3) optionally, repeatingsteps (1) and (2) using the product from step (2) to obtain highergenerations of dendrimers.

The primary polyamine in the initial step (1) is preferably a diamine,such as, for example, 1,2-diaminoethane, 1,3-diaminopropane,1,4-diaminobutane or the like.

The invention also includes terminally monomaleated polyisobutyleneessentially free of unmaleated polyisobutylene, preferably less than 10percent by weight of the polyisobutylene.

The invention also embraces the star-branched polymeric materialprepared by the method described above which is essentially free ofunreacted polyisobutylene. By using a mixture of two or morepolyisobutylenes of different molecular weights the branches on eachdendrimer core can have mixed lengths.

Moreover, the present invention includes star branched polymericmaterial comprising a hydrophilic dendrimer core with mixed branches offunctionalized polyolefin and the polyisoolefin. The polyolefin branchescan be a polymer or copolymer of ethylene, propylene, butylene or thelike. Preferably, the polyisoolefin is polyisobutylene.

Moreover, the present invention includes star branched polymericmaterial comprising a hydrolytically stable dendrimer core with branchesof polyolefins such as polyethylene, polypropylene, ethylene-propylenecopolymers, and the like. The polyolefin is preferably polypropylenemade with a metallocene catalyst.

The present invention also provides a composition comprising a blend ofpolyolefin, such as polyethylene, polypropylene, ethylene-propylenecopolymers and the like, with a star-branched polymer comprising adendrimer core and polyisoolefin branches or the mixed branches. Thepolyolefin is preferably polypropylene, more preferably polypropylenemade with a metallocene catalyst.

The blend has particular utility in films with improved tear andpuncture resistance and controlled moisture/oxygen permeability.

DESCRIPTION OF THE INVENTION

One aspect of the invention comprises a method for preparingpolyisoolefin such as polyisobutylene which has a reactive ‘exo’terminal double bond chain end, and is essentially free of thenon-reactive ‘endo’ terminal double bond chain end. The method hasparticular advantage in functionalizing polyisobutylene to formsubstantially exclusive ‘exo’ reactive unsaturated groups, and to usehydrocarbon solvents for the functionalization reactions. Accordingly,polyisobutylene is referred to below for illustrative purposes only andas a preferred embodiment.

Halogen-terminated polyisoolefins are conventionally prepared bycarbocationically polymerizing isoolefins having from 4 to about 12carbon atoms in the presence of a halogenating agent according totechniques well known in the art. Briefly, the isoolefin is polymerizedusing halogenating initiators such as 2,4,4-trimethylpentyl chloridewith a Friedel-Crafts acid co-initiator such as BCl₃ or TiCl₄ inappropriate halohydrocarbon solvent such as methyl chloride, methylenechloride or the like. More detailed isoolefin polymerization techniquesfor obtaining a halogen-terminated polyisoolefin are described inFeinberg et al., Polymer Preprints, vol. 17, p. 797 (1976); Kennedy etal., Polymer Preprints, vol. 17, p. 194 (1976); Kennedy et al., Journalof Polymer Science, vol. 15, p. 2801 (1977); and Kennedy et al., Journalof Polymer Science, Polymer Chemistry Edition, vol. 18, p. 1523 (1980)which are incorporated herein by reference.

The polyisobutylene can be monohalogenated, but di-halogenated ortelechelic polyisobutylene is also known for example, from U.S. Pat. No.4,316,973 to Kennedy which is incorporated herein by reference.

In accordance with this invention, dehydrohalogenation of thehalogen-terminated polyisobutylene is conducted in the presence of astrong base represented by the formula RO-M wherein R represents analkyl group having at least 5 carbon atoms and M is an alkali metal. Thepreferred base is potassium t-pentoxide, and is referred to below forillustrative purposes only and as a preferred embodiment.

The dehydrohalogenation reaction is preferably conducted in an aliphaticsolvent such as hexane, cyclohexane, heptane, octane or the like.Solvents such as tetrahydrofuran (THF) are not employed because of thepotential for this solvent to form peroxides and produce undesirableside reactions. The dehydrohalogenation generally proceeds under refluxfor a period of time sufficient to substantially convert thehalogen-terminated polyisobutylene to vinylidene-terminatedpolyisobutylene (PIB-U), typically a period of several hours. Thereaction can be allowed to cool to room temperature, washed with aqueousmineral acid to remove potassium hydroxide, then with acetone/water,preferably in a volume ratio of from 1:4 to 9:1, until neutral to removet-pentanol. The product can be dried with a hygroscopic material such asCaCl₂. Residual solvent can be evaporated, for example, at elevatedtemperature under vacuum.

The weight average molecular weight of the PIB-U can range from about500 to about 500,000 and greater depending upon the desired end use. Forbranches on a dendrimer core, the PIB preferably has a molecular weightup to 50,000, more preferably from 500 to 20,000.

According to the present invention the PIB-U is functionalized forreactivity with amine. The PIB-U can have the reactive terminalunsaturation converted, for example, to succinic anhydride. Succinicanhydride groups are preferred, and thus conversion of the PIB-U tosuccinic anhydride-terminated PIB (PIB-SA) is preferred. PIB-SA isreferred to below for illustrative purposes only and as a preferredembodiment.

The PIB-U is converted to PIB-SA by heating a mixture of PIB-U andmaleic anhydride in approximately stoichiometric proportions, typicallywith a slight excess of maleic anhydride, generally to a temperaturefrom 170° to 250° C. This ene reaction can also be effected at elevatedpressure with or without a conventional ene catalyst.

The PIB-SA can be grafted to any dendrimer core having primaryamine-terminated branches. A preferred dendrimer core is the dendriticmacromolecule described in U.S. Pat. No. 5,530,092 which is incorporatedherein by reference in its entirety. Briefly, the dendrimer core isprepared by reacting functional groups of a primary diamine withacrylonitrile or methacrylonitrile, reducing the incorporated nitrilegroups to amine groups, and if desired, reacting the amine groups withfurther acrylonitrile or methacrylonitrile units in a reiterativefashion to prepare succeeding generations in the branches emanating fromthe core.

As an example, 1,2-diaminoethane or 1,4 diaminobutane are reacted withacrylonitrile or methacrylonitrile to form the cyanide-terminated doubleMichael addition reaction product. This product is then hydrogenated toobtain a first generation product (G1) having 4 terminal amine groups.By reiterating the process, second, third and fourth generation products(G2, G3, G4) can be obtained which will respectively have 8, 16, and 32terminal amine groups and so on.

The PIB-SA is grafted onto the amine groups in the outer shell of thedendrimer by condensation at elevated temperature to form succinimidelinkages, with or without a solvent. Preferably, the PIB-SA anddendrimer are heated to the boiling point of the solvent, such astoulene, for a sufficient length of time to obtain a majority ofsuccinimide linkages, but with some succinamic acid linkages. This ispreferably followed by evaporation of the solvent and heating at90°-140° C., preferably 110°-120° C., under high vacuum for a period oftime effective to effect complete ring closure, i.e. conversion of thesuccinamic acid to succinimide.

The star-branched polymer comprising the dendrimer core and the PIBbranches via succinimide linkages has a number of uses, including, forexample, a viscosity modifier in organic liquid, as a pour pointdepressant in diesel fuel, as a motor oil additive, as a rheologymodifier or processing aid in thermoplastic compositions, as an adhesionpromoter between polar and nonpolar surfaces (especially by leaving someunreacted terminal amine groups in the dendrimer core by usingsubstoichrometric amounts of the PIB), and the like. Since thestar-branched polymer is generally free of unreacted PIB, it has agreater effectiveness per mass unit and less likely to have adverseeffects otherwise due to the presence of substantial amounts ofunreacted PIB.

Using mixed-molecular weight PIB results in branches of varying lengths.Using a mixture of hydrolytically stable dendrimer cores results invarying core sizes and a varying number of branches, e.g. G1 with G2and/or G3 dendrimers. Furthermore, by substituting some or all of thePIB branches with polyethylene, polypropylene or ethylene-propylenecopolymer branches, for example, the properties of the star-branchedpolymer can be further altered to tailor the star-branched polymer foruse in a wider range of systems, e.g. as a processing aid inpolyethylene, polypropylene and/or ethylene-polypropylene copolymercompositions. Mixed-branch star polymers are prepared, for example, byreacting the dendrimer core with a mixture of PIB-SA and maleatedpolyethylene, polypropylene and/or ethylene-polypropylene copolymer. Thestar branched polymer can also comprise the hydrolytically stabledendrimer core and branches of polyolefins.

The star-branched polymer is particularly effective in blends withpolyolefins as a means of controlling the transmission of moisture andgases through films made from the blends. The polyolefin can bepolyethylene, polypropylene, ethylene-polypropylene copolymer,polyisobutylene or the like. In a preferred embodiment the star-branchedpolymer is used in a blend with polypropylene made with a metallocenecatalyst. The blend can contain up to about 20 parts by weight of thestar-branched polymer, preferably 1 to 5 parts by weight, per 100 partsby weight of the polypropylene. The type and amount of star-branchedpolymer in the blend can be adjusted to obtain the desired balancebetween physical properties on the one hand, and moisture and oxygenpermeability on the other. Generally, the use of a higher generationstar-branched polymer (e.g. PIB-G2 versus PIB-G1) introduces more of thehydrophilic core material into the blend and increases moisture/gaspermeability. The polypropylene blends have markedly enhanced largestrain energy absorbing properties which are important in tear andpuncture resistance. The blends also have high elongation propertiessuitable for polypropylene fiber applications.

The blends can be prepared by solution or melt mixing using conventionalequipment. Melt mixing can be achieved by adding the star-branchedpolymer to the polypropylene in the final pellitization/granulationextrusion. Post-granulation blending can also be done on conventionalmelt mixing equipment such as a Banbury or Brabender mixer. Thepolypropylene is preferably melted prior to addition of thestar-branched polymer. The blends are formed into films or fibers usingconventional equipment and techniques.

EXAMPLE 1 Preparation of Exclusive ‘exo’ Double Bonded

Monochlorine-terminated polyisobutylene (PIB-Cl) was modified to obtainterminal succinic anhydride groups (PIB-SA). The PIB-Cl had Mn of 5000and Mw of 6050. 100% chlorine-terminated polymer was confirmed by ¹HNMR. The PIB-Cl (28.5 g) was placed in a reaction flask with 200 ml of0.35 molar potassium t-pentoxide (t-PeOK) in cyclohexane and refluxedunder nitrogen for 36 hours. The reaction product was washed with 10%HCl, water and acetone/water (9:1) until neutral, dried under CaCl₂,filtered and dried under vacuum at 90° C. for 2 days. Yield was 25 g. ¹HMNR at 300 MHZ showed a quantitative 100% conversion to externalunsaturated terminal groups (PIB-U).

EXAMPLE 2

Three grams of PIB-Cl was dissolved in 20 ml dry heptane. The solutionwas clear. Twenty milliliters of potassium t-pentoxide was added. Thesolution was still clear and contained only one phase, indicatingmiscibility. The solution was refluxed for 30 hours in a 110° C. bathunder a nitrogen atmosphere. The product was washed with water once andfive times with 20% acetone-water (20/80). The water wash was neutral.The organic layer was distilled off and vacuum dried at 130° C. for 6hours. The viscous liquid was dried under vacuum at 65° to 70° C. for 2days. The recovered polymer (2.8 g) was analyzed by ¹H NMR and had peaksat 1.75 ppm, 1.95 ppm and 4.65-4.85 ppm indicative of CH₂—C(CH₃)═CH₂terminal groups. There was no peak at 5.15 ppm, indicating an absence ofthe undesirable ‘endo’ double bond, —CH═C(CH₃)₂.

COMPARATIVE EXAMPLE 1

The reaction of PIB-Cl with the alkoxide of Example 3 is repeated asabove using potassium t-butoxide instead of potassium t-pentoxide. Noreaction occurs when the solvent is cyclohexane, heptane or hexane.

COMPARATIVE EXAMPLE 2 Preparation of PIB Containing both ‘exo’ and‘endo’ Double Bonds Synthesized in Single Step

In this example, two PIB-U's were prepared. PIB-U1 of Mn 1000; PIB-U2 ofMn 2300 are prepared by carbocationic polymerization of isobutyleneusing BF₃-OEt₂ catalyst, which yield 85% ‘exo’ and 15% ‘endo’unsaturation, in both cases.

EXAMPLE 3 Preparation of PIB-SA

The PIB-U of Example 1 (22.5 g) and 5 g of maleic anhydride were placedin a 2-neck flask swept with nitrogen. The flask was heated to 190°-200°C. in a heating mantle with a magnetic stirrer under nitrogen atmospherefor 36 hours, and cooled to room temperature. Dry cyclohexane (200 ml)was added, heated with stirring for 30 minutes, and then filtered. Thefiltrate was evaporated to about 70 ml, and 300 ml acetone was addedwhile stirring. The mixture was warmed to 45°-50° C. while stirring for30 minutes, cooled to room temperature and acetone was decanted off.This acetone wash procedure was repeated twice. The polymer was driedunder vacuum at about 90° C. for one day. A slightly brown clear liquid(PIB-SA) was obtained (20 g). FTIR confirmed anhydride and ¹H NMRindicated quantitative conversion to PIB-SA.

COMPARATIVE EXAMPLE 3 Preparation of Partial PIB-SA

PIB-U1/2 prepared in Comparative Example 2 (1 mole equivalent of doublebond) and maleic anhydride (MA) (6 mole equivalents of double bond) wereplaced in a flask filled with argon. The flask was fitted with acondenser, and an argon bubbler at the top. The flask was heated to190°-200° C. in a metal bath, and the reaction was continued at thattemperature while stirring with a magnetic stirrer under argonatmosphere. At this temperature, the viscosity of the mixture (PIB-U1/2and melted MA) is low, and the magnetic stirrer is efficient for mixing.The reaction was continued for 21 hours, cooled, dissolved in dry hexane(15 gm/100 ml), and filtered to remove unreacted MA. Hexane wasevaporated out. The brown viscous mass was stirred with dry acetone (20gm/100 ml) at 40°-45° C. for 30 mins, allowed to cool, and acetone wasdecanted off. This was repeated twice to be sure to remove any traces ofunreacted MA. The light brown viscous product was then dried undervacuum at 90° C.-100° C. About 85% of ‘exo’ structure was converted tothe corresponding anhydride terminal group. Thus, the products were amixture of PIB-SA which contained PIB-SA (63%), and unreacted PIB-‘exo’double bond (22%) and PIB-‘endo’ double bond (15%) as confirmed fromFTIR.

EXAMPLE 4 Preparation of Star Branched Polymer

The PIB-SA of Example 3 was reacted with dendrimer (G1) obtained fromDSM to prepare a star-branched polymer. Ten grams of the PIB-SA wasdissolved in 90 ml toluene (dried over molecular sieve) in a 2-neckflask fitted with a gas bubbler. The solution was clear. Then 0.145 g ofthe G1 dendrimer was dissolved in 5 ml toluene in a vial and transferredto the 2-neck flask. The vial was rinsed with an additional 5 ml toluenewhich was also transferred to the 2-neck flask. The solution was gentlyrefluxed overnight while stirring under a nitrogen atmosphere. FTIR ofthe solution indicated formation of free acid (—COOH) and amide(—CONH—). The toluene was distilled off to obtain a light brown viscousproduct. The product was heated to 110°-120° C. under high vacuum forone day to complete the ring closure reaction, i.e. conversion ofsuccinamic acid to succinimide. FTIR analysis indicated quantitativesuccininide derivitization of the dendrimer and was supported by ¹H NMR.

EXAMPLE 5 Preparation of Star Branched Polymer

The PIB-SA (6 g) of Example 3 was dissolved in 60 ml dry toluene, and0.12 g of G2 dendrimer obtained from DSM was added. The solution wasrefluxed for 16 hours under a nitrogen atmosphere. The solvent wasdistilled off FTIR analysis indicated complete amine-anhydride reactionwith a majority of ring closure with some succinamic acid. The productwas dissolved in 60 ml cyclohexane, washed twice with water and thecyclohexane was distilled off The slight brown product was washed twicewith hot 60 ml acetone. The product was transferred to a vial and heatedto 110°-120° C. under high vacuum for 24 hours to effect complete ringclosure by conversion of succinamic acid to succinimide. The oven wascooled to room temperature and filled with nitrogen to take out thesamples. The product was a slightly brown viscous liquid.

EXAMPLE 6-11

A series of blends were made with two types of isotactic polypropyleneand the star branched polymer PIB-G1 of Example 4. The polypropyleneswere prepared with a metallocene catalyst (M-iPP) and Ziegler-Nattacatalyst (ZN-iPP). Typically, that weight average molecular weight, Mw,of such commercial isotactic polypropylene polymers are in the range of100,000 to 300,000. The polypropylene and PIB-G1 were dissolved in hotxylene (about 130° C.), precipitated in isopropanol and subsequentlydried under vacuum for 24 hours at about 80° C. Thin pads were made bymolding for testing. The specimens were tested in accordance withstandard ASTM D-432 procedures (Instron cross head speed 0.5 in./min;room temperature; notched specimen). The blend compositions and testingdata (average of four tests) are shown in Table 1.

TABLE 1 Composition and Physical Properties of PP/PIB-G1 Example 6 7 8 910 11 Composition (Parts by Weight) M-iPP 100 98 95 0 0 0 ZN-iPP 0 0 0100 98 95 PIB-G1 0 2 5 0 2 5 Notched Tensile Test (RT @ 0.5 in./min;average of 4) Modulus 247 246 230 213 249 231 (1000 psi) Tensile 4.204.14 4.00 3.75 4.26 3.99 Strength (1000 psi) Elongation (%) 11.9 18.325.4 31.7 22.2 15.9 Yield Strain 4.20 4.14 4.00 3.75 4.26 3.99 (1000psi) Yield 4.5 4.6 4.7 4.7 4.7 4.5 Elongation (%) Energy/ 114 164 196273 210 146 Thickness (lbs-in./in.)

These data show that the M-iPP blends have enhanced energy absorptionwithout significant loss in inherent strength.

EXAMPLE 12 & 13

Preparation and performance of star branched dendrimer of afunctionalized polyolefin (maleic anhydride grafted polypropylene,ma-PP) and a third generation (G-3) dendrimers.

In a laboratory scale Brabender mixer, 100 gm of Ma-PP polymer was addedand fluxed for about 10 minutes at 200° C. After completely molten about0.25 gm of hydrolytically stable G-3 dendrimer was added. The mixturewas allowed to mix for about 5 minutes to ensure homogeneity. Duringmixing, small amounts of anti-oxidants (irganox 1010-Ciba Geigy) wasadded to avoid PP degradation. Subsequently, the reacted material wascompression molded using a lab Carver press to obtain specimen forvarious tests.

The Ma-PP used in the experiment was an Exxon Chemical product soldunder the Trade name Exxelor. Its MFR was 54 as determined by thestandard ASTM test. The Mw and MWD of Ma-PP were about 110,000 and 2.3,respectively, as determined by GPC. The G-3 dendrimer used is made byDSM Netherlands. Its molecular weight is reported to be 1684 g/mole. Itschemical nomenclature is DAB(PA)16- 16 cascade: 1,4 diamino butane[4]:(1-azabuitylidene) 12: propylamine.

Physical properties of the parent Ma-PP are compared (Table 2) with thatof its reaction product with G-3 dendrimer. It can be readily noted thatgrafting of G-3 dendrimer had significantly enhance the physicalperformance of the Ma-PP parent polymers. It is specifically noted thatMFR of the blend has been dramatically reduced. The later indicates agrafting reaction of PP chains with each other through G-3 dendrimer.

TABLE 2 Composition Maximum (Ma-PP to MFR Yield Displace- G-3) parts by230° C.; Modulus x Stress, ment weight 2,16 10³, Pa Psi in Example 12100 54 153.5 3250 0.425 - Control Example 13 100 + 0.25 27 171 28550.371 - Invention

We claim:
 1. A hydrolytically stable polymeric material comprising ahydrolytically stable dendrimer core and polyolefin branches prepared inaccordance with a reiterative process comprising one or more repetitivesteps of: (a) reacting a diaminoalkane with an acrylonitrile to form acyanide-terminated reaction product, (b) hydrogenating the reactionproduct to obtain a first generation product (G1) amine terminateddendrimer, (c) reacting G1 with an acrylonitrile and hydrogenating toform a second-generation product (G2) amine terminated dendrimer, (d)reacting G1, or G2 or successive Gn, wherein n is greater than 2, with afunctionalized polyolefin and (e) recovering the polymeric materialhaving a hydrolytically stable dendrimer core and branches of polyolefinemanating from the outer shell of the dendrimer.
 2. The star branchedpolymeric material of claim 1 wherein the polyolefin is a polyisoolefin.3. The star-branched material of claim 2 wherein the polyisoolefin ispolyisobutylene.
 4. The star branched polymeric material of claim 3wherein at least two polyisobutylene branches have different molecularweights.
 5. The star branched polymeric material of claim 3 wherein thepolyisobutylene branches have a molecular weight between 500 and 20,000.6. The star branched polymeric material of claim 1 comprising a mixtureof dendrimer cores of at least 2 generations.
 7. The star branchedpolymeric material of claim 3 also comprising branches of polyethylene,polypropylene or ethylene-propylene copolymer.
 8. The star branchedpolymeric material of claim 1 wherein the polyolefin is a alpha-olefinpolymer.
 9. The process in accordance with claim 1 wherein n is 3 or 4.10. A hydrolytically stable polymeric material comprising ahydrolytically stable dendrimer core and polyolefin branches prepared inaccordance with a reiterative process comprising the one or morerepetitive steps of: (a) reacting a diaminoalkane with an acrylonitrileto form a cyanide-terminated reaction product, (b) hydrogenating thereaction product to obtain a first generation product (G1) amineterminated dendrimer, if reiterating, (c) reacting G1 with anacrylonitrile and hydrogenating to form a second-generation product (G2)amine terminated dendrimer, (d) reacting G1, or if reiterative the G2 orsuccessive Gn, wherein n is greater than 2, with a functionalizedpolyolefin and (e) recovering the polymeric material having ahydrolytically stable dendrimer core and branches of polyolefinemanating from the outer shell of the dendrimer.
 11. The process inaccordance with claim 9 wherein n is 3 or
 4. 12. A hydrolytically stablepolymeric material comprising a hydrolytically stable dendrimer core andpolyolefin branches, wherein the dendrimer core is a hydrogenatedcyanide-terminated dendrimer, and wherein the polyolefin branches aresuccinamide-terminated polyolefins.
 13. A hydrolytically stablepolymeric material comprising a hydrolytically stable dendrimer core andpolyolefin branches, wherein the dendrimer core is a hydrogenatedcyanide-terminated dendrimer resulting from the reaction of adiamino-alkane and acrylonitrile followed by hydrogenation, and whereinthe polyolefin branches are succinamide-terminated polyolefins resultingfrom the reaction of exo-terminated polyisobutylene and maleicanhydride.